TW201441011A - Method for producing polarizable laminated film and polarizing plate - Google Patents

Abstract

The present invention provides a method for producing a polarizable laminated film, and a method for producing a polarizing plate using the polarizable laminated film obtained by the aforesaid method. The method for producing the polarizable laminated film comprising: a coating liquid preparing step in which a coating liquid is prepared in a reservoir of a coating machine; a resin layer forming step in which, from the reservoir, through a coating head of the coating machine, the coating liquid is supplied and coated on single of both surfaces of a substrate film and obtain a laminated film; a stretching step in which the laminated film is stretched to obtain a stretched film; and a dyeing step in which the polarizable laminated film is obtained by dyeing the resin layer of the stretched film by dichroic dye to form polarizer layers; wherein, in the coating liquid preparing step and/or the resin layer forming step, the coating liquid is transported through a pipe at least one time, and a part of the coating liquid is taken out from the pipe.

Description

Method for producing polarizing laminated film and method for producing polarizing plate

The present invention relates to a method for producing a polarizing laminated film and a method for producing a polarizing plate.

The polarizing plate is widely used as a polarizing supply element in a liquid crystal display device, and as a polarizing detecting element. In the polarizing plate, a polarizing film containing a polyvinyl alcohol-based resin is bonded to a polarizing film containing a cellulose triacetate or the like through an adhesive, but in recent years, with a notebook type in a liquid crystal display device The expansion of mobile devices such as personal computers and mobile phones, and the expansion of large-scale televisions, etc., are required to be light and thin.

However, the polarizing film is produced by stretching and dyeing a germinal film of a polyvinyl alcohol-based resin (having a general thickness of about 75 μm), and the film thickness after stretching is generally about 30 μm. The film formation of the above is difficult because of the productivity of the film which is easily broken during stretching.

Therefore, a method for producing a laminated film or a polarizing plate having a polarizing layer is proposed, in which a polyvinyl alcohol-based resin layer is formed by applying a coating liquid containing a polyvinyl alcohol-based resin to a base film to obtain a laminated film. Thereafter, the laminated film is subjected to stretching and dyeing treatment to impart a polarizing function to the polyvinyl alcohol-based resin layer as a polarizer. For example, Japanese Laid-Open Patent Publication No. 2009-93074 (Patent Document 1) and JP-A-2011-150313 (Patent Document 2)).

Prior technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-93074

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2011-150313

When the method of forming a polarizer layer by applying a coating liquid containing a polyvinyl alcohol-based resin is used as described in the above Patent Documents 1 and 2, a polarizing film is produced as compared with a film from a polyvinyl alcohol-based resin. In this case, a thinner polarizer layer can be obtained, which is advantageous from the viewpoint of lightening and thinning of the polarizing plate.

However, the coating liquid containing a polyvinyl alcohol-type resin is easy to foam, and when a bubble is generated, the bubble of the polyvinyl alcohol-type resin does not easily disappear. The resin layer obtained by applying the coating liquid containing such a bubble to the base film contains a large amount of air bubbles, and the polarizing laminated film or the polarizing plate obtained by stretching and dyeing the laminated film obtained in this manner is It does not show good polarizing performance and appearance, so it is difficult to use as a product. Therefore, part of the substrate film coated with the bubble-containing coating liquid has to be discarded.

The present invention has been made to solve the above problems, and the object of the invention is to produce a polarizing laminated film or a polarizing plate comprising a step of forming a resin layer by applying a coating liquid containing a polyvinyl alcohol resin to a base film. In the method, there is provided a method for minimizing (shortening) a coating liquid containing bubbles when applying a coating liquid The amount (time) supplied from the coater to the substrate film can effectively reduce the loss of the substrate film.

The present invention contains the following items.

<1> A method for producing a polarizing laminated film, comprising: a coating liquid preparation step of preparing a coating liquid containing a polyvinyl alcohol-based resin in a storage tank of a coater; and a resin layer forming step The coating liquid is supplied and applied to at least one surface of the base film from the storage tank through the coating head of the coater, and then dried to form a polyvinyl alcohol-based resin layer to obtain a laminated film; a step of stretching the laminated film to obtain a stretched film; and a dyeing step of dyeing the polyvinyl alcohol-based resin layer of the stretched film by a dichroic dye to form a polarizer layer, thereby obtaining a polarizing layer In the coating liquid preparation step and/or the resin layer formation step, at least once, the coating liquid is transferred by a pipe and a part of the coating liquid is taken from the middle of the piping.

<2> The method according to <1>, wherein the coating machine includes: a first pipe that connects the storage tank and the coating head; and a second pipe that branches from the first pipe; The storage tank transfers the coating liquid to the coating head, and extracts a part of the coating liquid through the second pipe.

<3> The method of <2>, wherein a part of the coating liquid is taken out when the coating liquid is passed through the inner space of the first pipe having the inner space not filled with the coating liquid.

The method according to any one of <1> to <3> wherein the laminated film is stretched at a stretching ratio of more than 5 times.

The method of any one of <1> to <4> wherein the polyvinyl alcohol-based resin layer is formed on both surfaces of the base film in the resin layer forming step.

The method of any one of <1> to <5>, wherein the polyvinyl alcohol-based resin layer of the laminated film has a thickness of 3 to 30 μm.

The method of any one of <1> to <6>, wherein the base film is a polypropylene resin.

<8> A method for producing a polarizing plate, comprising: a step of producing a polarizing laminated film by the method according to any one of <1> to <7>; and laminating on the polarizing layer of the polarizing laminated film a step of obtaining a film by a protective film; and a step of peeling the base film from the bonded film.

According to the method of the present invention, since the loss of the substrate film can be reduced, the polarizing laminated film or the polarizing plate can be produced with good yield.

1‧‧‧Coating machine

2‧‧‧ storage tank

3‧‧‧ pump

4‧‧‧Filter

5‧‧‧Coating head

6‧‧‧1st piping

7‧‧‧2nd piping

(S10)‧‧‧ Coating solution preparation steps

(S20) ‧‧‧resid layer formation step

(S30) ‧ ‧ extension steps

(S40)‧‧‧Staining step

(S50) ‧‧‧Finishing steps

(S60)‧‧‧ peeling step

Fig. 1 is a flow chart showing a preferred embodiment of a method for producing a polarizing laminate film of the present invention and a method for producing a polarizing plate.

Fig. 2 is a schematic view showing an example of a configuration of a coater which is suitable for carrying out the method for producing a polarizing laminated film of the present invention and a method for producing a polarizing plate.

Hereinafter, a method for producing a polarizing laminated film of the present invention and a method for producing a polarizing plate will be described in detail with reference to the embodiments.

<Method for Producing Polarized Laminated Film>

Fig. 1 is a flow chart showing a preferred embodiment of a method for producing a polarizing laminate film of the present invention and a method for producing a polarizing plate. The method for producing a polarizing laminated film of the present embodiment sequentially includes the following steps [1] to [4].

[1] Coating liquid preparation step S10, in which a coating liquid containing a polyvinyl alcohol-based resin is prepared in a storage tank of a coater.

[2] Resin layer forming step S20, which is obtained by applying the coating liquid from a storage tank through a coating head of a coater and applying it to at least one surface of the base film, and drying it to form a polyethylene. An alcohol resin layer was obtained to obtain a laminated film.

[3] The step S30 is extended by stretching the laminated film to obtain a stretched film.

[4] A dyeing step S40 in which a polyvinyl alcohol-based resin layer of a stretched film is dyed by a dichroic dye to form a polarizer layer, thereby obtaining a polarizing laminated film.

At least one of the coating liquid preparation step S10 and the resin layer forming step S20 transfers the coating liquid through the piping at least once, and extracts a part of the coating liquid from the middle of the piping.

As will be described later, in the polarizing plate of the present embodiment, the protective film can be bonded to the polarizing layer of the polarizing laminated film obtained in the dyeing step S40 to obtain a bonded film (bonding step S50). Then, the base film is peeled off from the bonded film and removed (peeling step S60).

Hereinafter, each step of S10 to S40 provided in the method for producing a polarizing laminated film of the present embodiment will be described in more detail.

[1] Coating liquid preparation step S10

This step is a step of preparing a coating liquid containing a polyvinyl alcohol-based resin in a storage tank of a coater.

(coating liquid containing polyvinyl alcohol resin)

The coating liquid is preferably a polyvinyl alcohol-based resin solution obtained by dissolving a powder of a polyvinyl alcohol-based resin in a good solvent (for example, water). Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and a derivative thereof. Examples of the derivative of the polyvinyl alcohol resin include polyethylene formaldehyde, polyvinyl acetal, and the like, and a polyvinyl alcohol resin modified by using an olefin such as ethylene or propylene; and acrylic acid, methacrylic acid, A modified carboxylic acid of crotonic acid; a modified alkyl ester of an unsaturated carboxylic acid; and a modified acrylamide. The ratio of the modification is preferably less than 30 mol%, preferably less than 10 mol%. When the modification is more than 30 mol%, it becomes a problem that the dichroic dye is not easily adsorbed and the polarizing performance may be lowered. Among the above polyvinyl alcohol-based resins, a polyvinyl alcohol resin is preferably used.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably in the range of 100 to 10,000, preferably in the range of 1,000 to 10,000, more preferably in the range of 1,500 to 8,000, and most preferably in the range of 2,000 to 5,000. The average degree of polymerization can be determined by the method specified in JIS K 6726-1994 "Testing methods for polyvinyl alcohol". When the average degree of polymerization is less than 100, it is difficult to obtain a preferable polarizing performance, and when it is more than 10,000, the solubility in a solvent is deteriorated, and it is difficult to form a polyvinyl alcohol-based resin layer.

The polyvinyl alcohol-based resin is preferably a saponified product of a polyvinyl acetate-based resin. The degree of saponification is in the range of 80 mol% or more, and preferably 90 mol% or more, particularly 94 mol% or more. When the degree of saponification is too low, when it is used as a polarizing laminated film or a polarizing plate, water resistance and moist heat resistance may be insufficient. Further, it may be a completely saponified product (the degree of saponification is 100% by mole), but when the degree of saponification is too high, the dyeing speed is slow, and the production time may be lengthened in order to provide sufficient polarizing performance, or depending on the case. There is a case where a polarizing layer having sufficient polarizing properties cannot be obtained. Therefore, the degree of saponification is 99.5 mol% or less, and preferably 99.0 mol% or less.

The degree of saponification is a ratio of the acetoxy group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin of the raw material of the polyvinyl alcohol-based resin to a hydroxyl group by saponification treatment, in terms of a unit ratio. (Mole%) is expressed by the following formula: degree of saponification (% by mole) = [(hydroxyl number) ÷ (number of hydroxyl groups + number of acetate groups)] × 100.

The higher the degree of saponification, the more the ratio of hydroxyl groups is, and therefore the smaller the ratio of the acetate groups which hinder crystallization. The degree of saponification can be determined in accordance with the method specified in JIS K 6726-1994 "Testing methods for polyvinyl alcohol".

Examples of the polyvinyl acetate-based resin include copolymers other than polyvinyl acetate of a homopolymer of vinyl acetate and other monomers copolymerizable with vinyl acetate. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

An example of a commercially available product of a polyvinyl alcohol-based resin that can be suitably used is a product name, and includes "PVA124" (saponification degree: 98.0 to 99.0 mol%) and "PVA117" (KVARAY). Saponification degree: 98.0 to 99.0 mol%), "PVA117H" (saponification degree: 99.5 mol% or more), "PVA624" (saponification degree: 95.0 to 96.0 mol%) and "PVA617" (saponification degree: 94.5 to 95.5) Mohr %); "AH-26" (saponification degree: 97.0 to 98.8 mol%), "AH-22" (saponification degree: 97.5 to 98.5 mol%), "NH" manufactured by Nippon Synthetic Chemical Industry Co., Ltd. -18" (saponification degree: 98.0 to 99.0 mol%) and "N-300" (saponification degree: 98.0 to 99.0 mol%); "JC-33" made by Japan VAM & POVAL Co., Ltd. (saponification degree: 99.0 Mo More than 8% of the ear), "JM-33" (saponification degree: 93.5 to 95.5 mol%), "JM-26" (saponification degree: 95.5 to 97.5 mol%), "JP-45" (saponification degree: 86.5 to 89.5 mol%), "JF-17" (Saponification degree: 98.0 to 99.0 mol%), "JF-17L" (saponification degree: 98.0 to 99.0 mol%) and "JF-20" (saponification degree: 98.0 to 99.0 mol%).

The coating liquid may contain an additive such as a plasticizer or a surfactant as necessary. As the plasticizer, a polyhydric alcohol or a condensate thereof or the like can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the additive to be added is preferably 20% by weight or less of the polyvinyl alcohol-based resin.

(coating machine)

As the coater, those previously known can be appropriately selected and used. When an example of a coater is given, for example, a wire bar coater; a roll coater such as a reverse roll coater or a gravure coater; a die coater; a notch coater (comma) Coater); lip coater; spin coater; screen coater; spray type knife coater; dip coater; spray coater.

The coater has at least a coating head that supplies a coating liquid onto the substrate film and a storage tank that stores the coating liquid. A second diagram showing an example of a configuration of a coating machine which is suitable for carrying out the method for producing a polarizing laminated film of the present embodiment and the method for producing a polarizing plate is generally provided with a filter and a pump (also referred to as a pump). The filter removes dust or the like from the coating liquid, and the pump is used to transfer the coating liquid.

Further, in the coating machine 1 shown in Fig. 2, the coater 1 includes an application head 5 for supplying a coating liquid onto a substrate film, and a storage tank (TANK) 2, which For storing the coating liquid; the filter 4 is disposed in the front portion of the coating head 5 for removing dust and the like in the coating liquid; and the pump 3 is used for the storage tank 2 The coating liquid is supplied. The storage tank 2 and the coating head 5 are passed through the first piping The first pipe 6 is connected with the pump 3 and the filter 4 interposed therebetween. The first pipe 6 transfers the coating liquid from the storage tank 2 to the transfer pipe of the coating head 5. Further, the first pipe 6 is connected to the second pipe 7 branched between the filter 4 and the coating head 5.

The configuration and material of the coating head 5, the filter 4, and the first pipe 6 may be those of a coater. The composition and material of the pump 3 may be generally used in a coater, and in particular, a pump having a small amount of leaking gas, such as a single screw pump (Moineau pump) or a diaphragm pump (Diaphragm pump), may be suitably used. The structure and material of the storage tank 2 may be a general one of the coating machine. Further, the storage tank 2 may be a container, such as a can, a container, or the like, for storing or conveying the prepared coating liquid.

It is preferable that the discharge port of the storage tank 2 for discharging the coating liquid is provided in the lower portion of the storage tank 2. When the upper portion has a discharge port, especially when the viscosity of the coating liquid is high, the pump 3 system is easily loaded. Further, a defoaming treatment tank (a tank capable of performing vacuum defoaming or the like) may be used as the storage tank 2.

In this step, a coating liquid is prepared in the storage tank 2 of the coater 1. The preparation of the coating liquid can be carried out, for example, as one of the following.

(a) Transferring the coating liquid contained in the container for storage or transportation to the storage tank 2 by means of a pump or the like or by manual addition.

(b) The container itself for storing or transporting the prepared coating liquid is attached to the pump 3.

(c) connecting the storage tank 2 or the above-mentioned container connected to the pump 3 to another storage tank 2 or another container containing the coating liquid.

When the coating liquid is gradually reduced, the methods (a) to (c) above may be used when the coating liquid is replenished to the storage tank 2. In the method of the above (a), since the coating liquid is injected from above by manual addition, bubbles are easily generated to prevent it by using a pump or the like. It is preferable to splash the liquid on the liquid surface of the coating liquid and to suppress generation of bubbles as much as possible. The composition and material of the pump and the piping to be used are not particularly limited. As described above, when the coating liquid is transferred by piping, the liquid to be described later can be performed.

[2] Resin layer forming step S20

This step is a step of obtaining a laminated film by forming and applying a coating liquid from the storage tank 2 of the coater 1 through the coating head 5 to form a polyvinyl alcohol-based resin layer on at least one side of the base film. The polyvinyl alcohol-based resin layer is a layer of a polarizer layer after the extending step S30 and the dyeing step S40. The polyvinyl alcohol-based resin layer can be formed by applying a coating liquid on one surface or both surfaces of a base film and drying the coating layer. According to this method, since the thickness of the polyvinyl alcohol-based resin layer and the polarizing plate layer can be made small, it is advantageous to reduce the thickness of the polarizing laminated film and the polarizing plate.

According to the present invention, since the liquid is pumped, the coating liquid containing no bubbles (or the generation of bubbles is extremely small) can be supplied to the substrate film from the initial stage of the coating step of applying the coating liquid to the substrate film. .

(substrate film)

The base film may be composed of a thermoplastic resin, and particularly preferably a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, and elongation. Specific examples of the thermoplastic resin include, for example, a polyolefin resin such as a chain polyolefin resin or a cyclic polyolefin resin (such as a decene-based resin); a polyester resin; and a (meth)acrylic resin. a resin; a cellulose ester resin such as cellulose triacetate or cellulose diacetate; a polycarbonate resin; a polyvinyl alcohol resin; a polyvinyl acetate resin; a polyarylate resin; Resin; polyether oxime resin; polyfluorene resin; polyamine resin; polyimine resin; and mixtures, copolymers and the like.

The base film may be a single layer structure including a resin layer containing one or more thermoplastic resins, or a resin laminated layer including one or two or more thermoplastic resins. Into a multi-layer structure.

Examples of the chain-like polyolefin resin include a homopolymer of a chain olefin such as a polyethylene resin or a polypropylene resin, and a copolymer containing two or more kinds of chain olefins. In order to easily and stably extend at a high rate, a base film comprising a chain polyolefin resin is preferred. In particular, the base film is composed of a polypropylene resin (a polypropylene resin of a propylene homopolymer, a copolymer mainly composed of propylene), and a polyethylene resin (a polyethylene resin of a homopolymer of ethylene). A copolymer of ethylene as a main component or the like is more preferable.

A copolymer mainly composed of propylene as an example of a thermoplastic resin constituting a substrate film, which is a copolymer of other monomers copolymerizable with propylene, is suitably used.

Examples of the other monomer copolymerizable with propylene include ethylene and an α-olefin. As the α-olefin, an α-olefin having 4 or more carbon atoms can be suitably used, and an α-olefin having 4 to 10 carbon atoms is preferable. Specific examples of the α-olefin having 4 to 10 carbon atoms, for example, a linear single such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene An olefin; a branched monoolefin such as 3-methyl-1-butene, 3-methyl-1-pentene or 4-methyl-1-pentene; vinylcyclohexane or the like. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer.

The content of the above other monomers is, for example, 0.1 to 20% by weight, preferably 0.5 to 10% by weight, based on the copolymer. The content of the other monomer in the copolymer can be determined by infrared (IR) spectroscopy in accordance with the method described on page 616 of the "Handbook of Polymer Analysis" (published by Kiyoshiya Shoten, 1995).

Among the above, as the polypropylene resin, a homopolymer of propylene, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer or a propylene-ethylene-1-butene random can be suitably used. Copolymer.

The stereoregularity of the polypropylene-based resin is preferably substantially isotactic or syndiotactic. A base film comprising a polypropylene-based resin having substantially uniform or syndiotactic stereoregularity is excellent in handleability and excellent in mechanical strength in a high-temperature environment.

The base film may be composed of one type of chain polyolefin resin, or may be composed of a mixture of two or more kinds of chain polyolefin resins, or may be a copolymer of two or more kinds of chain polyolefin resins. Composition.

The cyclic polyolefin-based resin is a general term for a resin which is polymerized by using a cyclic olefin as a polymerization unit, and is disclosed in Japanese Unexamined Patent Publication No. Hei No. Hei No. Hei. The resin described in the publication No. 122137 or the like. Specific examples of the cyclic polyolefin-based resin include a ring-opened (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and a chain olefin such as ethylene or propylene. (Representatively, a random copolymer), a graft polymer obtained by modifying the unsaturated carboxylic acid or a derivative thereof, and the like, and the like. In particular, a norbornene-based resin having a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer as a cyclic olefin is used.

The cyclic polyolefin-based resin is commercially available as various products. In the case of the commercial product of the cyclic polyolefin resin, "Topas" (available from TOPAS ADVANCED POLYMERS GmbH, available from POLYPLASTICS) and "ARTON" (JSR) System, "ZEONOR" (Japan ZEON (share) system), "ZEONEX" (Japan ZEON (share) system), "APEL" (Mitsui Chemical (share) system).

In addition, "S-SINA" (made by Sekisui Chemical Industry Co., Ltd.), "SCA40" (made by Sekisui Chemical Industry Co., Ltd.), and "ZeonorFlim" (Japan ZEON) are also available. A commercially available product of a cyclic polyolefin resin film formed by forming a film is used as a base film.

The base film may be composed of one type of cyclic polyolefin resin, or may be composed of a mixture of two or more kinds of cyclic polyolefin resins, or may be composed of a copolymer of two or more kinds of cyclic polyolefin resins.

The polyester resin is a resin having an ester bond, and is usually a polycondensate comprising a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include p-citric acid, isodecanoic acid, dimethyl p-nonanoate, and dimethyl naphthalene dicarboxylate. As the polyhydric alcohol, a divalent diol can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexane dimethanol.

As a representative example of the polyester resin, polyethylene terephthalate which is a polycondensate of citric acid and ethylene glycol can be mentioned. The polyethylene terephthalate-based crystalline resin is easily subjected to a treatment such as stretching before the crystallization treatment. If necessary, it may be crystallized by heat treatment such as stretching or stretching. Further, a copolymerized polyester which reduces the crystallinity (or becomes amorphous) by copolymerizing a skeleton of polyethylene terephthalate with another monomer can also be applied. Examples of such a resin include those obtained by copolymerizing cyclohexane dimethanol or isodecanoic acid. These resins are suitable for use because of their excellent extensibility.

Specific examples of the polyester-based resin other than the polyethylene terephthalate copolymer and the copolymer thereof include, for example, polybutylene terephthalate, polyethylene naphthalate, and polyethylene naphthalate. Ester, polytrimethylene terephthalate, Polypropylene naphthalate, polycyclohexane dimethyl phthalate, dimethyl polycyclohexane naphthalate, and the like.

The base film may be composed of one type of polyester resin, or may be composed of a mixture of two or more kinds of polyester resins, or may be composed of a copolymer of two or more kinds of polyester resins.

The (meth)acrylic resin is a resin having a compound having a (meth)acryl fluorenyl group as a main constituent monomer. Specific examples of the (meth)acrylic resin include, for example, poly(meth)acrylate such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate-( Methyl) acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl (meth) acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and A copolymer of an alicyclic hydrocarbon group-containing compound (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-(meth)acrylic acid decyl ester copolymer, etc.). It is preferred to use a poly(meth)acrylic acid C _1-6 alkyl ester such as poly(methyl) acrylate as a main component, and it is preferred to use methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight, of a methyl methacrylate-based resin.

The base film may be composed of one type of (meth)acrylic resin, or may be composed of a mixture of two or more kinds of (meth)acrylic resins, or two or more kinds of (meth)acrylic resins. Made up of copolymers.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose dipropionate, and the like. Further, examples of the copolymer and a part of the hydroxyl group which are modified by other substituents may be mentioned. Among these, cellulose triacetate (cellulose triacetate) is particularly preferred. There are many products sold in cellulose triacetate. It is also advantageous in terms of ease of access and cost. As an example of a commercially available product of cellulose triacetate, "FUJITAC TD80" (Fuji Film Co., Ltd.), "FUJITAC TD80UF" (Fuji Film Co., Ltd.), " FUJITAC TD80UZ" (Fuji Film Co., Ltd.), "FUJITAC TD40UZ" (Fuji Film Co., Ltd.), "KC8UX2M" (Konica Minolta Opto Co., Ltd.), and "KC4UY" (Konica Minolta Opto Co., Ltd.) Wait.

The base film may be composed of one type of cellulose ester resin, or may be composed of a mixture of two or more kinds of cellulose ester resins, or may be composed of a copolymer of two or more kinds of cellulose ester resins.

The polycarbonate resin is an engineering plastic containing a polymer which permeates a monomer unit through a carbonate group, and is a resin having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate resin constituting the base film may be a resin called modified polycarbonate or a copolymerized polycarbonate having improved wavelength dependency, which is a polymer skeleton which is modified to reduce the photoelastic coefficient.

Polycarbonate resins are sold in various products. As an example of the commercial product of the polycarbonate-based resin, "PANLITE" (made by Teijin Chemicals Co., Ltd.), "UPILON" (Mitsubishi Engineering Plastics Co., Ltd.), " SD POLYCA" (Sumitomo Dow Co., Ltd.), "CALIBRE" (Dow Chemical Co., Ltd.), etc.

The base film may be composed of one type of polycarbonate resin, or may be composed of a mixture of two or more kinds of polycarbonate resins, or may be composed of a copolymer of two or more kinds of polycarbonate resins.

Among the above, a polypropylene resin can be suitably used from the viewpoints of elongation, heat resistance and the like.

In the base film, in addition to the above thermoplastic resin, it may be added Any suitable additive. Examples of such an additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a color former. The content of the thermoplastic resin in the substrate film is preferably from 50 to 100% by weight, more preferably from 50 to 99% by weight, still more preferably from 60 to 98% by weight, still more preferably from 70 to 97% by weight. When the content of the thermoplastic resin in the base film is less than 50% by weight, the high transparency and the like which the thermoplastic resin originally has cannot be sufficiently exhibited.

The thickness of the base film can be appropriately determined, and is usually preferably from 1 to 500 μm, more preferably from 1 to 300 μm, even more preferably from 5 to 200 μm, particularly preferably from 5 to 5, in terms of workability such as strength and workability. 150 μm is the best.

(Drying of coating layer and polyvinyl alcohol-based resin layer)

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) can be set according to the kind of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C or higher. The drying time is, for example, 2 to 20 minutes.

The polyvinyl alcohol-based resin layer may be formed only on one side of the base film, or may be formed on both sides. When it is formed on both sides, since the curl of the film which may be generated when the polarizing laminated film or the polarizing plate is produced can be suppressed, and two polarizing plates can be obtained from one polarizing laminated film, in terms of production efficiency of the polarizing plate, It is also beneficial.

The thickness of the polyvinyl alcohol-based resin layer of the laminated film is preferably 3 to 30 μm, more preferably 5 to 20 μm. When the polyvinyl alcohol-based resin layer having the thickness in the range is obtained, the polarizing sheet layer having a good dichroic dye and excellent polarizing performance and a sufficiently small thickness can be obtained through the stretching step S30 and the dyeing step S40 which will be described later. When the thickness of the polyvinyl alcohol-based resin layer is more than 30 μm, the thickness of the polarizer layer is More than 10μm. When the thickness of the polyvinyl alcohol-based resin layer is less than 3 μm, the thickness tends to be too thin after stretching and the dyeability tends to be deteriorated.

Before the application of the coating liquid, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, at least the surface of the base film on the side where the polyvinyl alcohol-based resin layer is formed may be subjected to corona treatment and plasma treatment. Processing, flame treatment, etc.

In order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, a polyvinyl alcohol-based resin layer can be formed by passing a primer layer or an adhesive layer on the base film.

(primer layer)

The primer layer can be formed by applying a coating liquid for forming a primer layer on the surface of the base film and then drying it. The coating liquid for forming a primer layer contains a component which exhibits a certain strength of adhesion between both the base film and the polyvinyl alcohol-based resin layer. The coating liquid for forming a primer layer usually contains a resin component and a solvent which impart such adhesion. As the resin component, a thermoplastic resin excellent in transparency, heat stability, and elongation is preferably used, and examples thereof include a (meth)acrylic resin and a polyvinyl alcohol resin. In particular, a polyvinyl alcohol-based resin which can provide a good adhesion can be suitably used.

Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and a derivative thereof. Examples of the derivative of the polyvinyl alcohol resin include polyethylene formaldehyde, polyvinyl acetal, and the like, and a polyvinyl alcohol resin is modified by using an olefin such as ethylene or propylene; and acrylic acid, methacrylic acid, or the like is used. The unsaturated carboxylic acid of crotonic acid is modified; the alkyl ester of an unsaturated carboxylic acid is used for upgrading; the acrylamide is used for upgrading. Among the above polyvinyl alcohol-based resins, a polyvinyl alcohol resin is preferably used.

As the solvent, a general organic solvent and an aqueous solvent which can dissolve the above resin component can be usually used. When an example of a solvent is given, for example, benzene, toluene, An aromatic hydrocarbon of xylene; a ketone such as pyruvic acid, methyl ethyl ketone or methyl isobutyl ketone; an ester such as ethyl acetate or isobutyl acetate; such as dichloromethane or trichloroethylene; Chlorinated hydrocarbons of chloroform; alcohols such as ethanol, 1-propanol, 2-propanol, 1-butanol. However, when a primer layer is formed using a coating liquid for forming a primer layer containing an organic solvent, the base film may be dissolved, and the solubility of the base film may be considered, and the solvent is preferably selected. When considering the influence on the environment, it is preferred to form a primer layer from a coating liquid using water as a solvent.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the coating liquid for forming a primer layer. The cross-linking agent is appropriately selected from known ones such as an organic system and an inorganic system in accordance with the type of the thermoplastic resin to be used. Examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, and metal-based crosslinking agents.

As the epoxy-based crosslinking agent, any one of a one-liquid curing type and a two-liquid curing type may be used, and examples thereof include ethylene glycol diepoxypropyl ether, polyethylene glycol diepoxypropyl ether, and glycerin II. Or triepoxypropyl ether, 1,6-hexanediol diepoxypropyl ether, trimethylolpropane triepoxypropyl ether, diepoxypropyl aniline, diepoxypropylamine, and the like.

Examples of the isocyanate crosslinking agent include toluene diisocyanate, hydrogenated toluene diisocyanate, trimethylolpropane-toluene diisocyanate adduct, triphenylmethane triisocyanate, and methylene bis(4-phenylmethane) three. Isocyanate, isophorone diisocyanate, and the ketone oxime block or phenol block or the like.

Examples of the dialdehyde-based crosslinking agent include glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, maleic aldehyde, and sebacaldehyde.

Examples of the metal-based crosslinking agent include metal salts, metal oxides, metal hydroxides, and organometallic compounds. As a metal salt, a metal oxide, The metal hydroxide may, for example, be a salt of a metal having a valence of two or more valences such as magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, lanthanum, boron, zinc, copper, vanadium, chromium or tin. Oxides and hydroxides.

The organometallic compound is a compound in which an organic group is directly bonded to a metal atom or a structure in which at least one organic group is bonded to an oxygen atom or a nitrogen atom in a molecule. The organic group means a group having at least one or more valences of a carbon element, and may be, for example, an alkyl group, an alkoxy group, a fluorenyl group or the like. Further, the bonding means not only a covalent bond but also a coordination bond by coordination of a chelate compound or the like.

Suitable examples of the organometallic compound include an organic titanium compound, an organic zirconium compound, an organoaluminum compound, and an organic ruthenium compound. The organometallic compound may be used alone or in combination of two or more.

Examples of the organic titanium compound include, for example, tetra-n-butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetrakis(2-ethylhexyl) titanate, and tetramethyl titanate. Raw titanates; such as titanium acetate pyruvate, titanium tetraacetate pyruvate, titanium polyacetylate pyruvate, titanium octylene glycolate, titanium lactate, titanium triethanolamine, ethyl ethyl hydrazine Titanium chelates of titanium acetate; titanium hydrides such as titanium hydroxystearate.

Examples of the organic zirconium compound include zirconium n-propionate, zirconium n-butyrate, zirconium tetraethate pyruvate, zirconium acetoacetate, zirconium diethylpyruvate, and diethyl acetoacetate. Zirconium and the like.

Examples of the organoaluminum compound include aluminum acetylacetonate and an organic acid aluminum chelate compound. The organic ruthenium compound may, for example, be a compound in which a ligand exemplified above in the organotitanium compound and the organozirconium compound is bonded to ruthenium.

In addition to the above low molecular crosslinking agent, a polymer crosslinking agent such as a methylolated melamine resin or a polyamide resin may be used. In the case of a commercial product of a polyamide resin, "Sumirez Resin 650 (30)" and "Sumirez Resin 675" (all of which are trade names) sold by the Takada Chemical Industry Co., Ltd. )Wait.

When a polyvinyl alcohol-based resin is used as the resin component for forming the primer layer, a polyamide solvent, a methylolated melamine resin, a dialdehyde crosslinking agent, a metal chelating agent compound crosslinking agent can be suitably used. Etc. as a crosslinking agent.

The ratio of the resin component to the crosslinking agent in the coating liquid for forming a primer layer is from 0.1 to 100 parts by weight based on the kind of the resin component, the type of the crosslinking agent, and the like, based on 100 parts by weight of the resin component. The range of the right and left may be appropriately determined, and it is particularly preferable to select from the range of about 0.1 to 50 parts by weight. Further, the coating liquid for forming a primer layer preferably has a solid content concentration of about 1 to 25% by weight.

The thickness of the primer layer is preferably from about 0.05 to 1 μm, more preferably from 0.1 to 0.4 μm. When it is thinner than 0.05 μm, the adhesion improving effect of the base film and the polyvinyl alcohol-based resin layer is small, and when it is thicker than 1 μm, it is disadvantageous in that the polarizing laminated film and the polarizing plate are thinned.

The method of applying the coating liquid for forming a primer layer to the substrate film is the same as in the case of the coating liquid for forming a polyvinyl alcohol-based resin layer. The primer layer is applied to the surface on which the coating liquid for forming a polyvinyl alcohol-based resin layer is applied (on one side or both sides of the base film). The drying temperature and drying time of the coating layer containing the coating liquid for forming a primer layer can be set according to the kind of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is Above 80 ° C is preferred. The drying time is, for example, 30 seconds to 20 minutes.

(pumping)

In the coating liquid preparation step S10 and the resin layer forming step S20 described above, the coating liquid is transferred through the piping at least once, and a part of the coating liquid is taken from the middle of the piping.

In the coating liquid preparation step S10, the case where the liquid is to be applied means that the coating liquid containing the bubbles is supplied from the coating head 5 to the coating layer of the resin layer forming step S20. The case of the possibility of the substrate film is specifically exemplified as follows.

(A) When the coating liquid supplied into the storage tank 2 or the coating liquid in the above-mentioned container connected to the pump 3 is observed, the biting of the air bubbles can be observed (for example, using the above method (a) When the cloth liquid is transferred to the storage tank 2, it is easy to mix with air to generate bubbles).

(B) When the supply of the coating liquid is performed by the above method (c) (when the storage tank 2 or the container is changed, it is easy to mix with air to generate bubbles).

By performing the pumping, it is possible to effectively reduce (short) the coating liquid containing the bubbles from the coater 1 when the coating of the coating liquid of the step S20 is formed in the next resin layer, particularly at the start of coating. Since the coating head 5 is supplied in an amount (time), the loss of the base film can be greatly reduced, and the polarizing laminated film or the polarizing plate can be produced with good yield.

In the case where the liquid layer is to be applied in the resin layer forming step S20, there is a possibility that the coating liquid containing the bubbles is supplied from the coating head 5 to the base film when the coating liquid is applied. Specifically, when the coating is started, the coating liquid is transferred by the inner space of the first pipe 6 and the inner space which is not filled with the coating liquid. The situation, etc. Since the liquid is also applied in such a case, the amount (time) of the coating liquid containing the bubbles from the coating head 5 of the coater 1 can be effectively reduced (shortened), so that the substrate can be greatly reduced. The polarizing laminate film or the polarizing plate can be produced with good yield in the loss of the film.

The liquid extraction system may be carried out only in the coating liquid preparation step S10, or may be carried out only in the resin layer forming step S20, or in both steps.

In the coating liquid preparation step S10, when the coating liquid is transferred to the storage tank 2 by a pipe or the like by means of the above-described method (a), a branch can be set in advance and can be branched from the branch. A portion of the coating liquid is taken.

In the coating liquid preparation step S10, when bubbles are formed in the coating liquid in the storage tank in preparation, a part of the coating liquid can be taken from between the storage tank 2 of the coater 1 and the coating head 5. In the resin layer forming step S20, a part of the coating liquid in the coater 1 may be taken from between the storage tank 2 of the coater 1 and the coating head 5. Hereinafter, a specific aspect of extracting a part of the coating liquid from between the storage tank 2 of the coater 1 and the coating head 5 will be described in more detail with reference to Fig. 2 .

The coating liquid is supplied from the storage tank 2 to the base film through the coating head 5. The extraction of the coating liquid containing a large number of bubbles is performed on the upstream side of the coating head. In other words, while the pump 3 is operated, the coating liquid is transferred from the storage tank 2 toward the coating head 5, and a part of the coating liquid is taken out at a position between the storage tank 2 and the coating head 5. Specifically, as shown in FIG. 2, the second pipe 7 branched from the first pipe 6 can be used in advance at any position between the storage tank 2 and the coating head 5, and the second pipe can be transmitted through the second pipe. 7 method of extracting the coating liquid. The coating liquid extracted from the second pipe 7 may be subjected to a defoaming treatment as necessary, and then returned to the storage tank 2 for reuse.

When a flow path switching means such as a three-way cock is provided at a connection point between the first pipe 6 and the second pipe 7, the switching between the liquid pumping and the coating on the base film can be easily performed. The determination of the switching is to determine the state of the bubble of the coating liquid discharged from the second pipe 7 by visual observation (for example, when the coating liquid not containing the bubble is discharged, the liquid is stopped and switched to the coating. The visual judgment on the substrate film or the like can also be performed by an automatic controller.

The position where the first pipe 6 and the second pipe 7 are connected should be as close as possible to the position of the coating head 5, so that the coating liquid can reduce the possibility of bubble generation from the position to the coating head 5, as shown in Fig. 2. It is shown that it is more preferable to be disposed on the downstream side of the filter 4 (between the filter 4 and the coating head 5). When the second pipe 7 is connected to the upstream side of the filter 4, the bubble is generated when the coating liquid is supplied again to the filter 4 after the completion of the liquid pumping. In order to prevent such a situation, when the second pipe 7 is connected to the upstream side of the filter 4, it is preferable to perform the air removal treatment in the filter 4 after the liquid is pumped. Further, between the storage tank 2 and the coating head 5, two or more branch points of the second pipe 7 and the second pipe 7 may be provided.

The pipe shape and material of the second pipe 7 are not particularly limited as long as they do not interfere with the flow of the coating liquid in the first pipe 6, and may be generally used as a pipe.

[3] Extension step S30

This step is a step of stretching a laminated film including a base film and a polyvinyl alcohol-based resin layer to obtain a stretched film. The stretching ratio of the laminated film can be appropriately selected in accordance with the required polarizing characteristics, and is preferably more than 5 times and 17 times or less, more preferably more than 5 times and not more than 8 times the original length of the laminated film. When the stretching ratio is 5 times or less, the polyvinyl alcohol-based resin layer is not sufficiently aligned, and the degree of polarization of the polarizing sheet layer may not be sufficiently improved. On the other hand, when the stretching ratio is greater than 17 times, The film is liable to be broken at the time of stretching, and the thickness of the stretched film is required to be thinner than necessary, in the case where the workability and workability are lowered in the subsequent step. The extension process is generally a uniaxial extension.

The extension process is not limited to one-stage extension, and can also be performed in multiple stages. At this time, all of the multi-stage stretching treatment may be continuously performed before the dyeing step S40, or the stretching treatment after the second stage or the dyeing treatment and/or the crosslinking treatment of the dyeing step S40 may be simultaneously performed. As described above, when the stretching treatment is performed in multiple stages, it is preferable to carry out the stretching treatment so that the total length of all the stretching treatments is greater than 5 times.

The stretching treatment may be a longitudinal extension extending in the film length direction (film conveyance direction), or a lateral extension or oblique extension extending in the film width direction. Examples of the longitudinal stretching method include stretching between rolls extending by a roll, compression and extension, extension using a chuck (clip), and the like. Examples of the lateral stretching method include a tenter method and the like. The stretching treatment may be any one of a wet stretching method and a dry stretching method, and it is preferable to use a dry stretching method in view of selecting a stretching temperature from a wide range.

The elongation temperature may be set to a temperature higher than the flowability of the polyvinyl alcohol-based resin layer and the substrate film as a whole, preferably [the melting point of the substrate film -30] ° C to [the melting point of the substrate film + 30 The range of ° C is preferably [the melting point of the substrate film -30] ° C to the [melting point of the substrate film + 5 ° ° C), more preferably [the melting point of the substrate film - 25 ° ° ° ° ° ° [substrate film The melting point] °C range. When the base film contains a plurality of resin layers, the above melting point means the highest melting point among the melting points exhibited by the plurality of resin layers.

When the elongation temperature is lower than [the melting point of the substrate film -30] ° C, it is not easy to achieve a high magnification extension of more than 5 times, or the fluidity of the substrate film is too low to cause elongation. Processing has a tendency to become difficult. When the stretching temperature is more than [the melting point of the base film + 30] ° C, the fluidity of the base film is too large to cause elongation to become difficult. Since it is easier to achieve a high stretching ratio of more than 5 times, the stretching temperature is within the above range, more preferably 120 °C or higher. When the stretching temperature is 120 ° C or more, even if the stretching ratio is more than 5 times, there is no difficulty in the stretching treatment.

The heating method of the laminated film as the elongation treatment is a section heating method (for example, a method of heating in an extension section of a heating furnace adjusted to a predetermined temperature by blowing hot air); when it is extended by using a roller, the heating roller The method of the cylinder itself; the heater heating method (the method of providing an infrared heater, a halogen heater, a plate heater or the like on the upper and lower sides of the laminated film and heating by radiant heat). In the method of extending between rolls, from the viewpoint of uniformity of elongation temperature, a section heating method is preferred. At this time, the two pairs of nip rolls may be disposed in the temperature-adjusted extension section or may be disposed outside the extension section. In order to prevent the build-up film from adhering to the nip roller, it is preferable to set it outside the extension section.

Further, the extension temperature means the ambient temperature in the section (for example, in the heating furnace) in the section heating method, and the ambient temperature in the furnace when the heater heating method is also performed in the furnace. Moreover, the heating method of the drum itself means the surface temperature of the drum.

It is also possible to provide a preheating step of preheating the laminated film before the extending step S30. As the preheating method, the same method as the heating method in the elongation treatment can be used. When the stretching treatment method is the extension between the rolls, the preheating system can be performed at any point before, during, and after passing through the nip rolls on the upstream side. When the extension treatment is such that the heat roller is extended, it is preferable to perform preheating at a time point before passing through the heat roller. The extension treatment is preferably performed when the extension of the collet is used, and the preheating is performed at a time before the distance between the collets is enlarged. The preheating temperature is in the range of -50 ° C to ± 0 ° C of the extension temperature. Preferably, the range of [extension temperature - 40] ° C to [extension temperature - 10] ° C is more preferable.

Further, after the extending process of the extending step S30, a heat fixing process step may be provided. The heat-fixing treatment performs heat treatment at a temperature higher than the crystallization temperature while holding the end portion of the stretched film with a clip and maintaining the tensile force. The crystallization of the polyvinyl alcohol-based resin layer can be promoted by the heat setting treatment. The temperature of the heat setting treatment is preferably in the range of -0 ° C to -80 ° C of the elongation temperature, and more preferably in the range of [extension temperature - 0] ° C to [extension temperature - 50 ° ° C.

[4] Dyeing step S40

This step is a step of dyeing a polyvinyl alcohol-based resin layer of a stretched film with a dichroic dye to adsorb and align it to form a polarizer layer. A polarizing laminated film having a polarizing plate layer on one or both of the base film can be obtained through this step.

Specific examples of the dichroic dye include iodine and a dichroic organic dye. Specific examples of the dichroic organic dye include, for example, RED BR, RED LR, RED R, PINK LB, RUBIN BL, BORDEAUX GS, SKYBLUE LG, LEMON YELLOW, BLUE BR, BLUE 2R, NAVY RY, GREEN LG, VIOLET LB , VIOLET B, BLACK H, BLACK B, BLACK GSP, YELLOW 3G, YELLOW R, ORANGE LR, ORANGE 3R, SCARLET GL, SCARLET KGL, CONGO RED, BRILLIANT VIOLET BK, SUPRA BLUE G, SUPRA BLUE GL, SUPRA ORANGE GL, DIRECT SKYBLUE, DIRECT FAST ORANGE S, FAST BLACK, etc. The dichroic dye system may be used alone or in combination of two or more.

The dyeing step can be carried out by immersing the entire stretched film in a solution (dyeing solution) containing a dichroic dye. As the dyeing solution, a solution obtained by dissolving the above dichroic dye in a solvent can be used. As a solvent for the dyeing solution, usually Water may be used, and an organic solvent compatible with water may be further added. The concentration of the dichroic dye of the dyeing solution is preferably from 0.01 to 10% by weight, more preferably from 0.02 to 7% by weight, still more preferably from 0.025 to 5% by weight.

When iodine is used as the dichroic dye, it is preferred to further add the iodide to the dye solution containing iodine because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. . The concentration of the iodide in the dyeing solution is preferably from 0.01 to 20% by weight. Among the iodides, potassium iodide is preferably added. When potassium iodide is added, the ratio of iodine to potassium iodide is in a weight ratio, preferably in the range of 1:5 to 1:100, more preferably in the range of 1:6 to 1:80, in the range of 1:7 to 1. The range of :70 is even better.

The immersion time of the stretched film in the dyeing solution is usually in the range of 15 seconds to 15 minutes, preferably 30 seconds to 3 minutes. Further, the temperature of the dyeing solution is preferably in the range of 10 to 60 ° C, more preferably in the range of 20 to 40 ° C.

Further, in the dyeing step S40, the stretching film may be further subjected to an elongation treatment. As an embodiment of the present embodiment, the following aspects and the like are exemplified: 1) After the stretching treatment is performed at a lower magnification than the target in the above-described stretching step S30, and in the dyeing treatment in the dyeing step S40, the total stretching ratio is used. In the case where the target magnification is performed, the stretching treatment is performed. When the crosslinking treatment is performed as described later, the crosslinking step is performed in the stretching step S30 at a lower magnification than the target, and then in the dyeing step. In the dyeing treatment of S40, the stretching treatment is performed until the total stretching ratio does not reach the target magnification, and then the stretching treatment is performed in the crosslinking treatment so that the final total stretching ratio becomes the target magnification.

The dyeing step S40 may be carried out after the dyeing treatment, and then carried out Cross-linking processing steps. The crosslinking treatment can be carried out by immersing the dyed film in a solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, a conventionally known one can be used, and examples thereof include a boron compound such as boric acid, borax, glyoxal, and glutaraldehyde. The crosslinking agent may be used alone or in combination of two or more.

The crosslinking solution may specifically be a solution in which a crosslinking agent is dissolved in a solvent. As the solvent, for example, water may be used, but an organic solvent compatible with water may be further contained. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of 1 to 20% by weight, more preferably in the range of 6 to 15% by weight.

The crosslinking solution may contain an iodide. By the addition of iodide, the polarizing performance in the plane of the polarizer layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. . The concentration of the iodide in the crosslinking solution is preferably from 0.05 to 15% by weight, more preferably from 0.5 to 8% by weight.

The immersion time of the dyed film in the crosslinking solution is usually from 15 seconds to 20 minutes, preferably from 30 seconds to 15 minutes. Further, the temperature of the crosslinking solution is preferably in the range of 10 to 90 °C.

Further, the crosslinking treatment can be carried out simultaneously with the dyeing treatment by formulating a crosslinking agent in the dyeing solution. Further, the stretching treatment may be performed in the crosslinking treatment. The specific aspect in which the elongation treatment is carried out in the crosslinking treatment is as described above.

After the dyeing step S40, it is preferable to perform the washing step and the drying step before the bonding step S50 to be described later. The washing step usually contains a water washing step. The water washing treatment can be carried out by immersing the film after the dyeing treatment or the crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually in the range of 3 to 50 ° C, preferably 4 to 20 ° C. The immersion time in water is usually 2 to 300 Seconds, preferably 3 to 240 seconds.

The washing step may be a combination of a water washing step and a washing step by an iodide solution. Further, the washing liquid used in the water washing step and/or the washing treatment by the iodide solution may suitably contain, for example, methanol, ethanol, isopropanol, butanol or propanol in addition to water. Liquid alcohol.

As the drying step performed after the washing step, any appropriate method such as natural drying, air drying, and heat drying may be employed. For example, when heat-dried, the drying temperature is usually from 20 to 95 ° C, and the drying time is usually from about 1 to 15 minutes. The polarizing laminate film obtained as described above can be used as a polarizing element as it is, and can also be used as an intermediate material for producing a polarizing plate including a polarizer layer and a protective film.

The thickness of the polarizer layer having the polarizing laminate film is 10 μm or less, preferably 7 μm or less. By setting the thickness of the polarizing plate layer to 10 μm or less, a thin polarizing laminated film can be formed.

<Method of Manufacturing Polarizing Plate>

The method for producing a polarizing plate of the present invention comprises, in order, a preparation step of preparing the above-mentioned polarizing laminated film, and a bonding step S50 of bonding a protective film to the polarizing layer of the polarizing laminated film to obtain a sticker. And a peeling step S60 which peels and removes a base film from a bonding film.

[5] Fitting step S50

In this step, a protective film is bonded to the polarizer layer of the polarizing laminate film, that is, on the surface opposite to the substrate film side of the polarizer layer to obtain a bonded film. The protective film can be bonded to the polarizer layer using an adhesive or an adhesive. When the polarizing layer film has a polarizer layer on both surfaces of the base film, it is usually applied to the polarizing layers on both sides. Self-adhesive protective film. At this time, the protective films may be the same kind of protective film or may be a heterogeneous protective film.

(protective film)

The protective film may be, for example, a polyolefin-based resin containing a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a decene-based resin); for example, cellulose triacetate or diacetate fiber Cellulose ester-based resin; such as polyethylene terephthalate, polyethylene naphthalate, polyester butadiene phthalate; polycarbonate resin; (meth) acrylic a resin; or a film of such a mixture, copolymer or the like. Examples of the commercially available products which can be used for the cyclic polyolefin resin, the film thereof, and the cellulose triacetate are as described above.

The protective film may be a protective film that has an optical function such as a retardation film or a brightness enhancement film. For example, a resin film containing the above material is stretched (uniaxially stretched or biaxially stretched), or a liquid crystal layer or the like is formed on the film, and a retardation film which can impart an arbitrary retardation value is used.

An optical layer such as a hard coat layer, an antiglare layer, or an antireflection layer may be formed on the surface opposite to the polarizer layer of the protective film. The method of forming the optical layers on the surface of the protective film is not particularly limited, and a well-known method can be used. The optical layer may be formed in advance on the protective film before the bonding step S50 is performed, or may be formed after the bonding step S50 or after the peeling step S60 described later.

When the protective film is bonded to the polarizer layer, plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment for improving the adhesion of the polarizer layer to the surface of the polarizer layer of the protective film can be performed. Surface treatment (easily followed by treatment) such as saponification treatment, especially for plasma treatment, corona treatment or saponification treatment. For example, when the protective film contains a cyclic polyolefin resin, it is usually subjected to plasma treatment. Or corona treatment. Further, when a cellulose ester-based resin is contained, it is usually saponified. As the saponification treatment, for example, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be mentioned.

The thickness of the protective film is preferably thin, but when it is too thin, the strength is lowered and the workability is poor. On the other hand, when it is too thick, there is a problem that the transparency is lowered, or the aging time required after the bonding is lengthened. Therefore, the thickness of the protective film is preferably 90 μm or less, preferably 5 to 60 μm, more preferably 5 to 50 μm. Moreover, from the viewpoint of thinning of the polarizing plate, the total thickness of the polarizing plate layer and the protective film is preferably 100 μm or less, preferably 90 μm or less, and more preferably 80 μm or less.

(adhesive)

As the adhesive, a water-based adhesive or a photocurable adhesive can be used. The water-based adhesive agent may, for example, be an adhesive containing a polyvinyl alcohol-based resin aqueous solution or an aqueous two-liquid urethane-based latex adhesive. In particular, when a cellulose ester-based resin film obtained by surface treatment (hydrophilization treatment) such as saponification treatment is used as the protective film, it is preferred to use a water-based adhesive containing a polyvinyl alcohol-based resin aqueous solution.

As the polyvinyl alcohol-based resin, in addition to the vinyl alcohol homopolymer obtained by saponifying the polyvinyl acetate of the homopolymer of vinyl acetate, vinyl acetate and other monomers copolymerizable therewith may be used. The polyvinyl alcohol-based copolymer obtained by subjecting the copolymer to saponification, or a modified polyvinyl alcohol-based polymer obtained by partially modifying the hydroxyl groups. The aqueous binder may contain an additive such as a polyvalent aldehyde, a water-soluble epoxy compound, a melamine-based compound, a zirconia compound, or a zinc compound. When a water-based adhesive is used, the thickness of the adhesive layer obtained therefrom is usually 1 μm or less.

Applying a water-based adhesive to the polarizer layer of the polarizing laminate film and/or Further, the film is bonded to the protective film through the adhesive layer, and it is preferable to carry out the bonding step by pressurizing and adhering using a bonding roll or the like. The coating method of the water-based adhesive (the same applies to the photocurable adhesive) is not particularly limited, and a casting method, a wire bar coating method, a gravure coating method, and a comma coater can be used. A previously known method such as a method, a doctor plate method, a die coater method, a dip coating method, a spray coating method, or the like.

When a water-based adhesive is used, it is preferable to carry out a drying step of drying the film in order to remove the water contained in the aqueous binder after the above-described bonding. The drying system can be carried out, for example, by introducing the film into a drying furnace. The drying temperature (temperature of the drying oven) is preferably from 30 to 90 °C. When it is less than 30 ° C, the polarizer layer tends to be easily peeled off from the protective film. Further, when the drying temperature is higher than 90 ° C, there is a concern that the polarizing performance of the polarizing sheet layer is deteriorated due to heat. The drying time can be set to about 10 to 1000 seconds, and from the viewpoint of productivity, it is preferably 60 to 750 seconds, more preferably 150 to 600 seconds.

After the drying step, the aging step of aging for about 12 to 600 hours may be carried out at room temperature or at a temperature slightly higher than the temperature, for example, about 20 to 45 °C. The curing temperature is generally set to be lower than the drying temperature.

The above-mentioned photocurable adhesive agent is an adhesive which is cured by irradiation with an active energy ray such as ultraviolet rays, and examples thereof include those containing a polymerizable compound and a photopolymerization initiator; those containing a photoreactive resin; Adhesive resin and photoreactive cross-linking agent. Examples of the polymerizable compound include a photopolymerizable monomer such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer; and a photopolymerizable monomer. Oligomers and the like. Examples of the photopolymerization initiator include neutral freedom by irradiation of active energy rays such as ultraviolet rays. A substance of an active species of a radical, an anionic radical, or a cationic radical. As the photocurable adhesive containing a polymerizable compound and a photopolymerization initiator, those containing a photocurable epoxy monomer and a photocationic polymerization initiator can be suitably used.

When a photocurable adhesive is used, after performing the above-described bonding, a drying step is performed as necessary (a photocurable adhesive is used when a solvent is contained, etc.), and a photocurable adhesive is applied by irradiating an active energy ray. Hardening step of hardening. The light source of the active energy ray is not particularly limited, and is preferably an active energy ray having a light-emitting distribution at a wavelength of 400 nm or less. Specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, and a black light can be suitably used. Lamps, microwaves, mercury lamps, halogenated metal lamps, etc.

Then the light-curing light irradiation intensity of the agent, the agent-based composition may then be appropriately determined in accordance with the light-curing, irradiation of an active area of the effective wavelength of the polymerization initiator is 0.1 to the intensity of 6000mW / cm ² of The mode setting is better. When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time is not excessively long, and when it is 6000 mW/cm ² or less, heat generated by the light source and heat generated by curing of the photocurable adhesive cause photocurable adhesive yellow. There is less concern that the polarizer and the polarizer layer are deteriorated.

The light irradiation time of the photocurable adhesive can be appropriately determined in accordance with the composition of the photocurable adhesive, and is preferably set so that the integrated light amount is 10 to 10000 mJ/cm ² , wherein the integrated light amount is as described above. The product of the intensity of the illumination and the irradiation time is expressed. When the total amount of light is 10 mJ/cm ² or more, the amount of the active species derived from the polymerization initiator can be sufficiently increased to carry out the curing reaction more reliably, and when the amount is 10000 mJ/cm ² or less, the irradiation time is not excessively long and can be maintained. Good productivity.

Further, the thickness of the adhesive layer after the active energy ray irradiation is usually about 0.001 to 5 μm, preferably 0.01 to 2 μm, preferably 0.01 to 1 μm.

(adhesive)

The adhesive which can be used for the bonding of the protective film usually contains an acrylic resin, a styrene resin, an anthrone-based resin or the like as a matrix polymer, and here, an isocyanate compound, an epoxy compound, an anthracycline ( Adhesive composition of aziridine) compound crosslinker. It is also possible to use an adhesive layer which further contains fine particles and exhibits light scattering properties.

The thickness of the adhesive layer may be from 1 to 40 μm, and it is preferably applied in a thin range within a range not impairing workability and durability, and specifically, it is preferably from 3 to 25 μm. A thickness of 3 to 25 μm has good workability, and is also suitable for suppressing dimensional change of the polarizer layer. When the adhesive layer is less than 1 μm, the adhesiveness is lowered, and when it is more than 40 μm, the adhesive is likely to overflow. In the method of bonding a protective film to a polarizer layer using an adhesive, an adhesive layer may be provided on the surface of the protective film, and then attached to the polarizer layer, or an adhesive layer may be provided on the polarizer layer. Protective film.

The method of forming the adhesive layer is not particularly limited, and an adhesive composition (adhesive solution) containing each component of the above-mentioned matrix polymer may be applied on a protective film surface or a polarizer layer and dried to form an adhesive layer. Thereafter, the protective film and the polarizer layer are bonded; after the adhesive layer is formed on the separation film (release film), the adhesive layer is transferred to the protective film surface or the polarizing film surface, and then the protective film is attached and The method of polarizing the film layer is carried out. When the adhesive layer is formed on the protective film surface or the polarizer layer, surface treatment such as corona treatment or the like may be performed on the protective film surface or the polarizer layer or on one or both sides of the adhesive layer as necessary.

[6] Stripping step S60

In this step, the base film is peeled off and removed from the bonded film obtained by bonding the protective film. The steps. Through this step, a polarizing plate in which a protective film is laminated on the polarizer layer can be obtained. The polarizing laminated film has a polarizer layer on both surfaces of the base film, and when the protective film is bonded to the polarizing film layers, the peeling step S60 can be obtained from one polarizing laminated film. Polarized plate.

The method of peeling and removing the base film is not particularly limited, and it can be peeled off by the same method as the peeling step of the separation film (release film) by the polarizing plate generally provided with the adhesive. The base film film may be directly peeled off immediately after the bonding step S50, or may be wound into a roll once after the bonding step S50, and peeled off while being rolled out in the subsequent step.

The polarizing plate manufactured as described above can also be used as an optical film in which another optical layer is laminated in practice. Further, the protective film may also have the function of such an optical layer. Examples of the other optical layer include a reflective polarizing film that transmits a certain polarized light and reflects polarized light having opposite properties; a film having an anti-glare function having a concave-convex shape on the surface; and a film having a surface anti-reflecting function; A reflective film having a reflective function on the surface; a semi-transmissive reflective film having both a reflective function and a transmissive function; a viewing angle compensation film.

As a commercial product of a reflective polarizing film that transmits a polarized light that reflects a certain kind of polarized light and reflects the opposite property, for example, "DBEF" (manufactured by 3M Company, and available from Sumitomo 3M in Japan) Acquired, "APF" (3M company, available from Sumitomo 3M (share) in Japan).

Examples of the viewing angle compensation film include an optical compensation film obtained by coating a liquid crystal compound on the surface of a substrate, and an optical compensation film comprising a polycarbonate resin; and a retardation film containing a cyclic polyolefin resin; Wait.

Corresponding to coating a liquid crystal compound on the surface of the substrate and aligning, For the commercial products of the fixed optical compensation film, "WV FILM" (Fuji FILM Co., Ltd.), "NH FILM" (JX Nippon Mining ENERGY Co., Ltd.), and "NR FILM" ("NR FILM") JX Nippon Mining Day ENERGY (share) system, etc.

"ARTON FILM" (made by JSR), "ESUSHINA" (made by Sekisui Chemical Industry Co., Ltd.), and "ZeonorFlim" are mentioned as a commercial item of the retardation film containing a cyclic polyolefin resin. (Japan ZEON (share) system) and so on.

Example

Hereinafter, the present invention will be more specifically described by showing examples, but the present invention is not limited by the examples.

<Example 1> (1) Fabrication of substrate film

A propylene/ethylene random copolymer containing about 5% by weight of an ethylene unit ("Sumitomo Chemical Co., Ltd.", "SUMITOMO NOBLEN W151", melting point Tm, was produced by co-extrusion using a multi-layer extrusion molding machine. A long substrate of a three-layer structure comprising a propylene-based homopolymer ("SUMITOMO NOBLEN FLX80E4" manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 163 ° C) on both sides of the resin layer of 138 ° C) membrane. The total thickness of the base film was 100 μm, and the thickness ratio of each layer (FLX80E4/W151/FLX80E4) was 3/4/3.

(2) Modulation of coating liquid

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, average saponification degree: 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a polyethylene having a concentration of 3% by weight. An aqueous alcohol solution. In the obtained aqueous solution, a crosslinking agent ("Sumirez Resin 650" manufactured by Tajika Chemical Industry Co., Ltd.) was mixed at a ratio of 1 part by weight based on 2 parts by weight of the polyvinyl alcohol powder to obtain a coating for forming a primer layer. liquid.

Further, polyvinyl alcohol powder ("PVA124" manufactured by KURARAY Co., Ltd., average polymerization degree 2400, average saponification degree: 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol having a concentration of 8 wt%. The aqueous solution is used as a coating liquid for forming a polyvinyl alcohol-based resin layer.

(3) Implementation of pumping

The coating liquid for forming a polyvinyl alcohol-based resin layer is transferred to a storage tank of the notch wheel coater using a pump. As shown in Fig. 2, the doctor blade applicator is provided with a second pipe for liquid separation between the filter for removing dust and the coating head, and can be switched by the first pipe by using a three-way cock. The destination of the liquid (coating head or second pipe). Next, in a state where the three-way cock is switched to the second pipe side, the pump of the notch wheel coater is operated, and the coating liquid in the storage tank is supplied to the coating head through the first pipe. The liquid discharged from the second pipe is performed. At the beginning of the discharge of the coating liquid, many bubbles can be confirmed with the naked eye, but as the amount of discharge increases, the amount of bubbles becomes small. When it is judged that the amount of bubbles is extremely small, the three-way cock is switched to supply the coating liquid to the coating head and the pump is stopped once.

(4) Formation of primer layer and polyvinyl alcohol-based resin layer

The corona treatment is carried out on one side of the substrate film prepared in the above (1) while being continuously conveyed, and the primer layer is continuously applied to the corona-treated side thereof using a micro gravure coater. The coating liquid for formation was dried at 60 ° C for 3 minutes to form a primer layer having a thickness of 0.2 μm. Then, the above-mentioned notch applicator which is filled with the coating liquid for forming a polyvinyl alcohol-based resin layer to the coating head is used, and the coating liquid is continuously applied to the primer layer by carrying the film. Further, it was dried at 90 ° C for 1 minute, 70 ° C for 3 minutes, and then at 60 ° C for 4 minutes, and a polyvinyl alcohol-based resin layer having a thickness of 11.0 μm was formed on the primer layer.

When the coating liquid for forming a polyvinyl alcohol-based resin layer was applied, the bubbles flowed out to the coated surface, but the flow immediately subsided, and the substrate film hardly caused any loss.

Further, the same treatment as described above was carried out on the surface of the base film opposite to the surface on which the polyvinyl alcohol-based resin layer was formed, and the primer layer and the polyvinyl alcohol-based resin layer were sequentially formed to form on both surfaces of the base film. A primer layer having a thickness of 0.2 μm and a polyvinyl alcohol-based resin layer having a thickness of 11.0 μm were used to obtain a layer structure including a polyvinyl alcohol-based resin layer/primer layer/base film/primer layer/polyvinyl alcohol-based resin layer. Laminated film.

When the coating liquid for forming a polyvinyl alcohol-based resin layer is applied to the surface of the base film on the opposite side, even if the liquid is not applied, the flow of bubbles at the start of coating is not observed. The coating liquid containing no bubbles is filled to the coating head.

(5) Extension of laminated film

While continuously transporting the laminated film obtained in the above (4), the free end uniaxially extends in the longitudinal direction (film transport direction) at an extension temperature of 160° C. using an inter-nip stretching method at 160° C. to form an extension. membrane. The thickness of the polyvinyl alcohol-based resin layer of the stretched film was 5.5 μm on one side and 5.3 μm on the other.

(6) Manufacture of polarizing laminated film

While continuously transporting the stretched film prepared in the above (5) while immersing in a warm water bath at 60 ° C for a residence time of 60 seconds, the dyeing solution at 30 ° C containing iodine and potassium iodide has a residence time of The polyvinyl alcohol-based resin layer was subjected to dyeing treatment by dipping for about 150 seconds, and then the excess dyeing solution was washed with pure water at 10 °C. Next, the crosslinking treatment was carried out by immersing in a crosslinking solution containing boric acid and potassium iodide at 76 ° C for a residence time of 600 seconds. Subsequently, it was washed by using pure water of 10 ° C for 4 seconds and drying at 80 ° C for 300 seconds. Light laminated film.

(7) Manufacture of polarizing plate

Polyvinyl alcohol powder ("KL-318" manufactured by KURARAY Co., Ltd., average polymerization degree: 1800) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3 wt%. In the obtained aqueous solution, a crosslinking agent ("Sumirez Resin 650" manufactured by Tajika Chemical Industry Co., Ltd.) was mixed at a ratio of 1 part by weight to 2 parts by weight of the polyvinyl alcohol powder to obtain an aqueous solution of an adhesive.

Then, while the polarizing laminated film produced in the above (6) is continuously conveyed, the aqueous solution of the adhesive is applied onto the polarizing plate layers on both surfaces, and then the saponification treatment is applied to the bonding surface by laminating the polarizing layer. Protective film [containing a transparent protective film of cellulose triacetate (TAC) ("KC4UY" manufactured by Konica Minolta Opto Co., Ltd.), thickness 40 μm], and obtained by crimping between a pair of bonding rolls TAC/polarized sheet/primer layer/substrate film/primer layer/polarized sheet/TAC layer structure bonding film.

Subsequently, the bonding film is peeled off from the interface between the substrate film and the primer layer to obtain a film comprising a TAC/polarizing sheet/primer layer/substrate film, and a polarizing plate comprising a primer layer/polarizing sheet/TAC. Thereafter, the base film was peeled off from the former film to obtain another polarizing plate. In the step of peeling off the base film, there is no problem such as film breakage.

<Comparative Example 1>

It was attempted that the liquid of the layer (3) of Example 1 was not applied to form a primer layer and a polyvinyl alcohol-based resin layer. When the coating liquid for forming a polyvinyl alcohol-based resin layer is applied, the bubbles are simultaneously discharged to the coating surface at the same time as the coating liquid. It takes 2 hours until the bubble flow subsides, resulting in a large loss of the base film. On the other hand, the substrate film is coated on the opposite side. When the coating liquid for forming a polyvinyl alcohol-based resin layer was applied, the outflow of bubbles at the start of coating could not be observed.

According to the method of the present invention, since the loss of the substrate film can be reduced, the polarizing laminated film or the polarizing plate can be produced with good yield.

(S10)‧‧‧ Coating solution preparation steps

(S20) ‧‧‧resid layer formation step

(S30) ‧ ‧ extension steps

(S40)‧‧‧Staining step

(S50) ‧‧‧Finishing steps

(S60)‧‧‧ peeling step

Claims (8)

A method for producing a polarizing laminated film, comprising: a coating liquid preparation step of preparing a coating liquid containing a polyvinyl alcohol resin in a storage tank of a coating machine; and a resin layer forming step by using the above The storage tank is supplied and applied to at least one surface of the base film by the coating head of the coater, and then dried to form a polyvinyl alcohol-based resin layer to obtain a laminated film; and an extending step; And extending the laminated film to obtain a stretched film; and a dyeing step of dyeing the polyvinyl alcohol-based resin layer of the stretched film by a dichroic dye to form a polarizing film layer, thereby obtaining a polarizing laminated film; In the coating liquid preparation step and/or the resin layer formation step, the coating liquid is transferred by piping at least once, and a part of the coating liquid is taken out from the middle of the piping. The manufacturing method according to claim 1, wherein the coating machine includes: a first pipe that connects the storage tank and the coating head; and a second pipe that branches from the first pipe While transferring the coating liquid from the storage tank toward the coating head, a part of the coating liquid is taken through the second piping. The production method according to the second aspect of the invention, wherein the liquid extraction step is performed when the coating liquid passes through the inner space of the first pipe having the inner space not filled with the coating liquid. The manufacturing method according to any one of claims 1 to 3, wherein the laminated film is stretched at a stretching ratio of more than 5 times. The production method according to any one of claims 1 to 4, wherein in the resin layer forming step, the polyvinyl alcohol-based resin layer is formed on both surfaces of the base film. The production method according to any one of claims 1 to 5, wherein the polyvinyl alcohol-based resin layer of the laminated film has a thickness of 3 to 30 μm. The production method according to any one of claims 1 to 6, wherein the base film comprises a polypropylene resin. A method of producing a polarizing plate, comprising: a step of producing a polarizing laminated film by using the manufacturing method according to any one of claims 1 to 7; and bonding on a polarizing layer of the polarizing laminated film a step of obtaining a film by a protective film; and a step of peeling the base film from the bonded film.